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In my Student Choice Project 1 offered by my Engineering Concepts class, I was given the chance to select a project of choice on something related to engineering. I decided to pick a project that not only would challenge both my mechanical and technological knowledge but would also benefit one of the robotics teams I oversee as Wheeler High School -- CircuitRunners Robotics' Director of Operations. I have already created three previous versions, so
Here is some specific information about the criteria and constraints regarding this project:
Overall Objective:
The overall goal is to build a mechanically functional differential swerve drivebase for use in the FTC environment. Programming will be developed externally from this project, but mechanically the drive must function as follows:
The drivebase must be rigid. The wheels and/or bearings must not shift or have a lot of play for consistent movement, especially in something like autonomous.
The drivebase must be precise. Repeatability with a GoBilda motor must be within 1 degree every time.
~432mm x 432mm so that the drivebase makes the most of the 18”x18” cube allowed in FTC.
Resources Required?
-Is there additional knowledge you will need?
-What materials will you need for this project?
-Are there any special tools you will need?
No additional knowledge, just time spent in CAD.
Fusion360, some CNC’d aluminum (from CR).
A CNC, from CR.
Some of the constraints that affected the project were the short timeframes required for such a complex project. This required me to cut corners in manufacturing as well as decide to not program the drivebase to tackle less at a time. In the first week of the allotted two weeks, I completed the design for the modules and finalized tolerancing in the 3D printed parts and allowed the final entire week for manufacturing. I completed this project alone, unlike others who worked together in their Student Choice Project.
Proposed Project:
The idea of differential swerve is to create a continuously rotating swerve module that does not need to unravel when it reaches its limits. In my journey to design and build differential swerve, I have created three previous modules that increasingly improved/worked better. Version 3, shown above, worked consistently enough to function as a visual piece, the fact that it made use of 3mm ball bearings meant that these bearings could more easily fall out and cause the system to fail to rotate smoothly.
In previous projects of my Engineering Concepts class, specifically our Woodworking sprint, I was able to practice precision work with my "Wood Block Frend" and created a dovetailed 2x4 joint that held strong and looked the part.
Designed, cut, and built with Fusion360, a table saw and careful measuring, and water-based stain as well as an oil based finish.
Our "CAM Smiley" assignment, which was actually a test to utilize our newly learned CAM skills based in Fusion360 gave me a strong foundation to be able to machine my aluminum plates using a Denford router.
Below is some of the work I put into building the drivebase:
Completed Drivebase (besides a few fixes)
Complete Module in CAD
Differential Swerve Plate
Cutouts in the plate allow for the custom bearing races to stay locked into place whilst providing smooth radial motion.
Completed Project - The Differential Swerve
In the completion of the project, I was able to learn a lot about 3d printing tolerances and the differences between using 3mm steel ball bearings and 4.3mm steel ball bearings. The end product was built well using aluminum GoBilda pattern U-Channel, as well as Low U-Channel, and used machined aluminum plates as well as custom 3D printed bearings to provide strong radial and axial strength in the system to combat the rigorous robot competition in the FIRST Tech Challenge competition.
I now have left to program the drivebase for use in competition (theoretically) and need to finalize some mechanical issues with the drivebase. Otherwise, the drivebase works in that in can handle loads (especially shock loads: it's been drop tested) as well as mechanically functioning as intended. Overall, one thing I might do differently is get the 3d printed parts printed in resin due to the higher print quality and tolerances. I'm proud of the work I've done here and hope it might get to see some use in future FTC competitions or at least inspire future roboticists to try to try complex designs as well.
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